Spinnerette



Dec. 12, 1967 J. s. COBB, JR 3,357,048

SPINNERETTE Filed May 27, 1966 '2 Sheets-Sheet 2 United States Patent Ofiiice 3,357,048 Patented Dec. 12, 1967 3,357,048 SPINNERETTE James Stanley Cobb, Jr., Martinsville, Va., assignor to E. L du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed May 27, 1966, Ser. No. 553,370 3 Claims. (Cl. 18-8) This invention relates generally to the melt spinning of hollow synthetic filaments and, more particularly, to improvements in the spinnerette nozzles through which such hollow filaments are spun.

Hollow filaments have been produced by extruding viscous organic materials through an interrupted annular slot and letting longitudinal edges of the extrudates coalesce below the spinnerette face (British patent specification No. 843,179). Final filament cross section depends not only on melt viscosity of the organic materials and quenching rate but also on discharge configuration, i.e., to form a good hollow filament it is essential that the segments coalesce. If coalescence does not occur at all times, poor quality filaments are produced. The latter and other difliculties encountered with complex orifices defined by interrupted annular slots have been recognized in the art (British patent specification No. 986,990) and avoided by overlapping or otherwise parallelizing the edges of two or more extrudates from a complex orifice. Preparation of these orifices is time consuming and expensive. Furthermore, they usually result in undesirably thick sections at the coalesced seams.

Reliable coalescence Without the formation of thick seams has been achieved according to the present inven tion by providing at least one nozzle extending through a spinnerette plate to a complex orifice defined by three or more slots. Each slot is U-shaped and opens toward an imaginary center of the complex orifice. The slot legs are rectilinear and have length dimensions suflicient to insure intersection of arcs swung from the inner ends of adjacent legs of adjacent slots. A common entrance hole leads to tapered and capillary lengths of the nozzle, each capillary length presenting one of the U-shaped slots.

Other advantageous features will become apparent in the following specification wherein reference is made to the accompanying drawings in which:

FIGURE 1 is a fragmentary view from the back of a spinnerette plate provided with nozzles according to the instant invention;

FIG. 2 is a sectional view taken on line IIII in FIG. 1;

FIG. 3 is a fragmentary view corresponding to FIG. 1 except for omission of tapered lengths above the capil laries; and

FIG. 4 is a fragmentary view of a plate having a complex orifice with four slots.

A typical spinnerette plate has a plurality of nozzles, one of which has been shown in FIGS. 1 and 2 to extend through plate from its back side 12 to a complex orifice in the face 14. As illustrated, nozzle 16 has an entrance hole 18 with a fiat bottom and communicates with three separate capillary lengths 20, 22, 24 through intermediate tapered lengths 21, 23, 25. Each capillary length has straight walls and presents one of the U-shaped slots or orifices shown in FIG. 3.

Entrance hole 18 can be formed by any of the wellknown methods of drilling and punching. At the completion, a flat-bottom counterbore remains. Tapered lengths 21, 23, 25 are stamped in the manner disclosed by Cobb in USP 3,017,789. Capillary lengths 20, 22, 24 are punched with two L-shaped tools which are mirror images, according to the indexing method disclosed by Kr-ummeck in USP 3,187,607.

When plate 10 is assembled with the other parts of a spinning pack and placed in operation, molten polymer is supplied to the back side 12, forced through entrance hole 18 and issues from capillaries 20, 22, 24. When the extrudates exit the slots, there is a tendency for the U shapes to flatten or open out. In this manner, edges of adjacent extrudates from adjacent U-shaped slots come together, coalesce and form a hollow filament.

A necessary feature of the nozzle configuration has been illustrated in FIG. 3 where rectilinear legs of the U-shaped slot defined by one capillary length have been designated 26, 28. The latter are connected by a rectilinear bight 30. Legs of the slot defined by a second capillary length have been designated 32, 34 and the bight by numeral 36. To insure that adjacent edges of extrudates issuing from the illustrated slots will come together, the slots are sized and positioned so that arcs swung on the adjacent legs of two slots intersect. This is illustrated in that, if an arc with a radius equal to the length of leg 26 is swung about the intersection between leg 26 and bight 30 and a second arc with a length equal to leg 32 is swung about the intersection of leg 32 and bight 36, these two arcs will intersect at point A. If these two arcs do not intersect, good coalescence cannot be assured.

The slot configurations shown in FIGS. 1 and 3 will produce trilobal-shaped hollow filaments. The four U- shaped slots illustrated in FIG. 4 will produce a tetralobal-shaped hollow filament. To insure good coalescence, and thus a satisfactory hollow filament, arcs swung on adjacent legs of any two slots intersect. This is illustrated at point B in FIG. 4.

While threeand four-slot configurations have been illustrated, it is of course apparent that higher numbers of slots in the complex orifice of a spinning nozzle will also produce hollow filaments. Good results can also be expected when the U-shaped slots have curvilinear bights, or when their rectilinear legs converge or diverge at small angles, as long as the criterion of intersecting arcs is met. Other variations and modifications of a similar nature will occur to those skilled in the art without departing from the spirit of my invention, which accordingly is intended to be limited only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A spinnerette plate having at least one nozzle extending therethrough to a complex orifice defined by at least three separate slots, each slot being U-shaped with a pair of rectilinear legs interconnected by a bight and opening toward the imaginary center of said orifice, said legs having lengths sufficiently great that imaginary arcs swung from the inner ends of adjacent legs of adjacent slots would intersect.

2. The spinnerette plate of claim 1 wherein said bights are rectlinear.

3. The spinnerette plate of claim 2 wherein said nozzle includes a common entrance hole leading to tapered and capillary lengths, each capillary length presenting one of said U-shaped slots.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 8/1960 Great Britain. 3/1962 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. A SPINNERETTE PLATE HAVING AT LEAST ONE NOZZLE EXTENDING THERETHROUGH TO A COMPLEX ORIFICE DEFINED BY AT LEAST THREE SEPARATE SLOTS, EACH SLOT BEING U-SHAPED WITH A PAIR OF RECTILINEAR LEGS INTERCONNEDTED BY A BIGHT AND OPENING TOWARD THE IMAGINARY CENTER OF SAID ORIFICE, SAID LEGS HAVING LENGTHS SUFFICIENTLY GREAT THAT IMAGINARY ARCS SWUNG FROM THE INNER ENDS OF ADJACENT LEGS OF ADJACENT SLOTS WOULD INTERSECT. 